Noun
1. a porous mass of interlacing fibers the forms the internal skeleton of various marine animals and usable to absorb water or any porous rubber or cellulose product similarly used
2. someone able to acquire new knowledge and skills rapidly and easily;
"she soaks up foreign languages like a sponge"3. a follower who hangs around a host (without benefit to the host) in hope of gain or advantage
4. primitive multicellular marine animal whose porous body is supported by a fibrous skeletal framework; usually occurs in sessile colonies